yes, underscores ("_") are not allowed in hostnames. Unfortunately it seems to be possible to use an underscore in the initial configuration of the hostname, but later the UI does not allow to store the hostname. Please try to repace the "_" by an "-" and try to save.

yes, underscores ("_") are not allowed in hostnames. Unfortunately it seems to be possible to use an underscore in the initial configuration of the hostname, but later the UI does not allow to store the hostname. Please try to repace the "_" by an "-" and try to save.